Externally cooled moving mold

ABSTRACT

A molding apparatus includes a moving mold for shaping molten plastic into product made within the moving mold. The moving mold is surrounded by an air block housing to define a cooling chamber exteriorly around the moving mold. At least one heat exchanger is located within the cooling chamber. The heat exchanger provides cooling air which is contained by the housing within the cooling chamber to act on and provide cooling of the moving mold.

FIELD OF THE INVENTION

The present invention relates to product molding apparatus of the typeusing mold block sections to form a moving mold.

BACKGROUND OF THE INVENTION

It is known in the molding business and particularly in the pipe moldingbusiness to use moving molds in forming the pipe for product. Thesemoving molds are formed by mold block sections that mate with oneanother to define a mold block tunnel. Molten plastic is fed from anextruder into the moving mold tunnel. The mold block sections thenseparate from one another along what is known as a return run to moveback to an up stream position for reentering the moving mold. Theplastic product or pipe emerges from the downstream end of the movingmold where the mold block sections separate from one another beforemoving to their return path.

As the mold block sections move in a downstream direction in the movingmold tunnel they pick up a large amount of heat from the molten plastic.This is detrimental to the cooling and shaping of the product in themoving mold. As such, it is important to attempt as much as possible tocool the mold block sections. Typically, this is done while the moldblock sections are mated with one another through the moving mold bysubjecting them to different cooling mediums. One cooling mediumaccording to conventional practice may be in the form of chilled waterrun through or onto the surfaces of the mold block sections. Anothercooling medium is cooling air run through the mold tunnel.

In the case where water is used to cool the mold block sections thereare generally problems created in controlling and drawing the water flow

In the case of introducing cooling air directly into the mold tunnelthere are problems associated with the location for the introduction ofthe air to get it into the mold tunnel. Further there is a problem withcooling of the actual extrusion equipment through which the air ispassed to get the air into the interior of the mold tunnel.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a molding apparatus having a moving moldwhich is subjected to cooling air outwardly around the moving mold. Thiseliminates the problems described above.

More particularly, the molding apparatus of the present inventionincludes a moving mold for shaping molten plastic into product madewithin the moving mold. The moving mold is surrounded by an air blockhousing to define a cooling chamber exteriorly around the moving mold. Asource of cooling air provides the cooling medium which is contained bythe housing within the cooling chamber to act on and provide cooling ofthe moving mold.

BRIEF DESCRIPTION OF THE DRAWINGS

The above as well as other advantages and features of the presentinvention will be described in greater detail according to the preferredembodiments of the present invention in which;

FIG. 1 is a side view of a complete molding apparatus according to apreferred embodiment of the present invention;

FIG. 2 is a sectional view through the moving mold region of theapparatus of FIG. 1;

FIG. 3 is an enlarged sectional view through the upstream end of themoving mold region of FIG. 1.

DETAILED DESCRIPTION ACCORDING TO THE PREFERRED EMBODIMENTS OF THEPRESENT INVENTION IN WHICH

FIG. 1 shows a pipe forming apparatus generally indicated at 1. Theentirety of this apparatus includes extrusion equipment 3 at theupstream end of the apparatus. This extrusion equipment provides moltenplastic which is fed to a molding region generally indicated at 5.Plastic product and in this case plastic pipe is shaped from the moltenplastic within the molding region. The plastic pipe then leaves themolding region for further setting or hardening within a cooler 17located downstream of the molding region 5.

The molding region itself comprises a pair of endless tracks of moldblock sections 7 and 9. These mold block sections as better seen in FIG.2 of the drawings meet to form a moving mold having a mold tunnel 10.The mold block sections then separate from one another along a returnrun before reentering the moving mold tunnel. In FIG. 2, mold blocksections 7 a from the upper track 7 mate with mold block sections 9 afrom the lower track 9 in forming the moving mold tunnel. FIG. 2 alsoshows mold block sections 7 b from the upper track and mold blocksections 9 b from the lower track in their open configuration as theymove along their respective return paths.

FIG. 3 of the drawings shows that the die equipment includes die tooling4 which feeds the molten plastic into the moving mold tunnel 10 wherethe plastic is actually shaped or formed into a pipe body.

Returning to FIG. 2 of the drawings, it will be seen that the movingmold comprising both the forward run and the return run for each of thetracks 7 and 9 is surrounded by an air block housing 11. This air blockhousing as described later in detail defines a cooling chamber 13exteriorly around the moving mold.

Cooling chamber 13 contains cooling air which is trapped within thecooling chamber to act on the exterior surfaces of the mold blocksections as they move through mold tunnel 10. The same trapped air alsoacts on the interior surfaces of the mold block sections when the moldblock sections are in an open configuration along a return run to themoving mold tunnel. More specifically, the cooling air acts on theexterior surfaces of mold block sections 7 a and 9 a and also acts onboth the interior and the exterior surfaces of mold block sections 7 band 9 b.

The cooling air can come from a number of different sources. Thesesources can be located either externally or internally of the air blockhousing. When the source of cooling is located externally of the housingit must be moved into the housing by air supply means such as ducting 15shown in FIGS. 1 and 2.

The source of cooling air can either be a manufactured source of air orit can be ambient air when the apparatus is situated in a relativelycold weather climate. A blower could be used to move the air through theducting from the supply source into the housing.

According to a preferred embodiment of the invention as shown in FIG. 2of the drawings air cooling units are provided directly within chamber13 surrounded by housing 11. The housing is preferably insulated toprevent heat loss through the housing. The housing can include slidinginsulated access doors 47 and 49 as well as an alarm sensor 51indicating opening of the access doors.

The cooling units such as heat exchangers 21 may for example be locatedto either side of the moving mold tunnel. Blowers 23 help to produce aheat exchange between the cooling units and the exterior surface of themoving mold tunnel. Further cooling units such as heat exchangers 25with associated blowers 27 may be provided above and below the open moldblock sections 7 b and 9 b along their return runs.

The above heat exchangers comprise any of numerous different types ofrefrigeration units to chill the air within the cooling chamber. Thischilled air is then moved onto the various different surfaces of themold block sections. The heated air coming off the mold block sectionsis in turn cooled by the heat exchangers. The air movement or turbulencewithin cooling chamber 13 enhances the cooling effect of the chilling orcooling air. This air is not allowed to escape the immediate vicinity ofthe mold block sections by virtue of it being entrapped within the airblock housing 11.

As earlier described, die tooling 4 feeds to the mold tunnel 10. Itenters the cooling chamber through mouth 12 of housing 11. This mouthclosely surrounds the die tooling to inhibit as much as possible theescape of cold air from chamber 13.

As will be appreciated from the description immediately above, dietooling 4 is itself exposed to the cooling air within chamber 13.However, cooling of the die tooling is adverse to the operation of theextruder. As such, a heater 31 having a plenum 33 feeds hot air directlyonto the exterior surface of die tooling 4 where the die tooling enterschamber 11. This hot air heating of the die tooling offsets the effectof the cooling air within the chamber on the die tooling.

The plastic pipe which leaves the molding region 5 of the apparatus willbe in a much firmer or more setup condition than it would be with aconventional moving mold. This is because the mold sections themselvesare kept much cooler than is normal practice. As such the mold blocksections are able to much more easily absorb the heat from the plasticfor the setting of the shape of the pipe in the molding region.

FIG. 1 as noted above also shows a product cooler 17 located inline withand downstream of mold tunnel 10. If this cooler is needed it providesadditional setting of the pipe outside of the mold region. In accordancewith a preferred embodiment of the invention cooler 17 is set up in amanner very similar to the actual mold region in that it may be providedwith its own supply of cooling air contained within the housing ofcooler 17. This cooling air is then trapped outwardly around and actsdirectly on the plastic of the pipe. This therefore provides anextremely rapid means for final cooling the pipe.

The drawings show the apparatus and in particular the moving mold asoperating in a horizontal direction. The invention i.e., the surroundingof the moving mold by an air block housing which contains cooling air isequally applicable to a plastic product forming apparatus having avertically orientated moving mold.

Although various preferred embodiments of the present invention havebeen described in detail, it will be appreciated by those skilled in theart that variations may be made without departing from the spirit of theinvention or the scope of the appended claims.

1. A molding apparatus (1) including a moving mold (10) for shapingmolten plastic into product made within said moving mold (10), saidmoving mold includes opposed mold blocks which meet in a closed moldblock configuration to define the moving mold in a forward run of saidmold blocks with said mold blocks separating to an open configuration ina return run of said mold blocks, said moving mold (10) being surroundedby an air block housing (11) in said forward run and said return run ofsaid mold blocks to define a cooling chamber (13) exteriorly around saidmoving mold (10), a source of cooling air (24), the cooling air (24)being contained by said housing (11) within said cooling chamber (13) toact on and provide cooling of said moving mold (10); said coolingchamber maintaining a trapped cooled air environment about said movingmold.
 2. Apparatus (1) as claimed in claim 1 wherein the source ofcooling air (24) comprises at least one cooling air unit (21, 25). 3.Apparatus (1) as claimed in claim 2 wherein said cooling unit (21, 25)is located internally of said air block housing (11).
 4. Moldingapparatus (1) as claimed in claim 3 including at least one blower (27)for circulating the cooled air (24) within said cooling chamber (13). 5.Apparatus as claimed in claim 2 wherein said cooling unit (21, 25) islocated externally of said air block housing (11), said apparatusincluding ducting (15) from said unit (21, 25) to said air block housing(11) and a blower (27) for moving the cooled air from said cooling unit(21, 25) through said ducting into said air block housing (11). 6.Molding apparatus as claimed in claim 1 wherein said source of coolingair (24) comprises cooled ambient air externally of said cooling chamber(13), said apparatus including ducting (15) from said housing (11) tothe source of cooling air.
 7. Molding apparatus as claimed in claim 6including blower means (15) to move the cooling air from said sourcethrough said ducting (15) into said cooling chamber (13).
 8. Apparatusas claimed in claim 1 wherein said air block housing (11) is insulatedto minimize heat loss of the cooling air (24) through said housing (11).9. Apparatus as claimed in claim 8 including access doors (47, 49)through said housing to said moving mold (10), said access doors (47,49) also being insulated.
 10. Apparatus as claimed in claim 9 includingan alarm (51) that indicates opening of said access doors (47, 49). 11.Apparatus as claimed in claim 1 including extruder die tooling feedinginto said moving mold (10) at one end of said housing (11) and furtherincluding a heater for heating said die tooling to offset effect of thecooling air in said cooling chamber on the die tooling.
 12. Apparatus asclaimed in claim 1 wherein said moving mold (10) comprises a pipecorrugator (7, 9).
 13. Apparatus as claimed in claim 1 wherein saidmoving mold (10) travels in a vertical direction through said coolingchamber (13).
 14. Apparatus as claimed in claim 1 wherein said movingmold (10) travels in a horizontal direction through said cooling chamber(13).
 15. Apparatus as claimed in claim 1 including a product cooler(17) downstream of said air block housing (11), said product cooler (17)being inline with and receiving the plastic product from said movingmold (10) and comprising a cooler housing around the product, and a heatexchanger within said cooler housing, said heat exchanger in said coolerhousing providing cooled air which is trapped within the cooler housingto act on the product after the product is released from the movingmold.
 16. Apparatus as claimed in claim 1 including a plurality of heatexchangers (21, 25) located within said cooling chamber (13), saidplurality of heat exchangers (21, 25) including first and second heatexchangers located to opposite sides of said moving mold (10). 17.Apparatus as claimed in claim 1 wherein said apparatus including firstand second heat exchangers (21) located to first and second sides ofsaid moving mold (10) and directed at said mold block sections (7, 9) inthe closed mold block configuration, and further includes third andfourth heat exchangers (25) to third and fourth sides of said movingmold and directed at said mold block sections (7, 9) in the open moldblock section configuration.